Yesterday, WPP announced that its organic global PR and public affairs revenues dropped 1.7% in 2013, although the group remains the largest PR holding company with $1.53 billion in revenues across its Burson-Marsteller, Ogilvy PR, Hill+Knowlton Strategies, Cohn & Wolfe, RLM Finsbury, and other PR brands.

WPP chief executive officer Martin Sorrell told me in Cannes last year that the agency services game isn't just about revenue, it is also about profit, and he explained that his PR division was still very profitable.

Yesterday's numbers put a little dent in that theory, with PR and PA profit down 0.4% year on year to 14.7%, although Sorrell told me via email that “although margins were down slightly, they're very robust.”

He also noted that the division's performance had improved in Q4 2013 and said “the Q4 improvement looks as though it will continue into 2014 - it did in January.”

Fleurot claimed MSL was number four globally in terms of revenue, though not necessarily in the US. And he echoed Sorrell in saying that “the pipeline is reasonably good at the moment.” I'd estimate MSL's global revenue number at about $500 million.

Edelman was up 11.4% last year to $741 million, though it is a private company and different financial reporting rules apply, so a direct apples to apples comparison is difficult (Sorrell describes Edelman's numbers as “opaque”.)

That means total global organic revenues across the big holding company PR networks and Edelman in 2013 added up to about $5.37 billion. So while WPP may be struggling to post positive growth in its PR firms, it still accounts for a significant chunk of the global PR pie.

With such variance in performance, these are clearly interesting times, and May's Agency Business Report will dig deeper into the raw data of almost 70 agencies to uncover the forensic detail behind the numbers and bring you the best-possible analysis of the PR agency world.